This invention belongs to the field of polycarbonates. In particular, it relates to polycarbonate-siloxane copolymers.
Historically, flame retardance systems for polycarbonate utilize low levels of additives to provide flame poisoning and anti-drip behavior. The most commonly employed flame poisons are organic bromine compounds, organophosphates, and salts of sulfonic acids. Drip inhibition is effectively provided by poly(tetrafluoroethylene), PTFE. Unfortunately, organic bromine derivatives are prohibited as eco-label additives; organophosphates are unsuitable because at the levels required for their effectiveness, they plasticize polycarbonate reducing both continuous use temperature and impact strength to impractical levels; and PTFE is unsuitable due to its crystallinity and refractive index mismatch with polycarbonate that preclude its use in transparent products. Salts of sulfonic acids provide flame retardant properties to polycarbonate in thick samples (3.2 millimeters) for normal or low flow polycarbonate, but for high flow products, they are ineffective without drip inhibitors.
Due to the restraints of flame retardant additives, it would be advantageous to have a polycarbonate with a minimum amount of flame retardant additives that also maintains transparent properties. Thus, a need exists for polycarbonates having flame retardancy and high flow while maintaining transparency.
The present invention provides a polycarbonate comprising residues of;
(a) at least one dihydric phenol; and
(b) at least one comonomer comprising a siloxane functional bis-phenol of the formula 
xe2x80x83wherein R is an alkyl group, cycloalkyl group, aryl group, fluoroalkyl group, or combinations thereof and n is in a range between 0 and 20;
(c) optionally, a branching agent; and
(d) optionally, a flame retardant.
The further embodiment of the present invention includes a method for producing a flame retardant polycarbonate comprising providing:
(a) at least one dihydric phenol; and
(b) at least one comonomer comprising a siloxane functional bis-phenol of the formula 
xe2x80x83wherein R is an alkyl group, cycloalkyl group, aryl group, fluoroalkyl group, or combinations thereof and n is in a range between 0 and 20;
(c) optionally, a branching agent; and
(d) optionally, a flame retardant wherein the resulting polycarbonate is transparent.
In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
The singular forms xe2x80x9ca,xe2x80x9d xe2x80x9can,xe2x80x9d and xe2x80x9cthexe2x80x9d include plural referents unless the context clearly dictates otherwise.
xe2x80x9cOptionalxe2x80x9d or xe2x80x9coptionallyxe2x80x9d means that the subsequently described event or circumstances may or may not occur, and that description includes instances where the event or circumstance occurs and instances where it does not.
xe2x80x9cBPAxe2x80x9d is herein defined as Bisphenol A or 2,2-bis(4-hydroxyphenyl)propane.
Unless otherwise stated, xe2x80x9cweight percentxe2x80x9d in reference to the composition of a polycarbonate in this specification is based upon 100 weight percent of the repeating units of the polycarbonate. For instance, xe2x80x9ca polycarbonate comprising 90 weight percent of BPAxe2x80x9d refers to a polycarbonate in which 90 weight percent of the repeating units are residues derived from Bisphenol A or its corresponding derivative(s). Corresponding derivatives include, but are not limited to, corresponding oligomers of the diphenols; corresponding esters of the diphenol and their oligomers; and the corresponding chloroformates of the diphenol and their oligomers.
The present invention provides a polycarbonate comprising residues of;
(a) a dihydric phenol; and
(b) at least one comonomer comprising a siloxane functional bisphenol of the formula 
xe2x80x83wherein R is an alkyl group, cycloalkyl group, aryl group, fluoroalkyl group, or combinations thereof and n is in a range between 0 and 20;
(c) optionally, a branching agent; and
(d) optionally, a flame retardant. Typically, R is a methyl group or a phenyl group
The utilization of the above monomers provides a useful combination of flame retardancy and high flow to the polycarbonate compositions as well as transparency. As used hereinafter, the term xe2x80x9cflame retardantxe2x80x9d means reduced or eliminated in tendency to ignite when exposed to a low-energy flame. As used hereinafter, the term xe2x80x9ctransparentxe2x80x9d means a maximum percent haze of 15 and a minimum percent transmission of 75. As used hereinafter, xe2x80x9chigh flowxe2x80x9d means a melt flow index no less than about 15 grams per 10 minutes at 300xc2x0 C. and 1.2 kilograms.
The siloxane functional bisphenol is typically utilized in proportions in a range between about 1 mole percent and about 10 mole percent relative to the amount of the dihydric phenol, and more typically, in a range between about 1 mole percent and about 5 mole percent of the dihydric phenol. In this regard, the use of the term xe2x80x9cresiduexe2x80x9d denotes that portion of the molecule or moiety which remains after the polycondensation reaction has taken place.
The dihydric phenol typically used in the present invention is 2,2-bis(4-hydroxyphenyl) propane (BPA). Optionally, the polycarbonate may be further comprised of other dihydric phenol compound residues in an amount up to about 10 to 50 weight percent of the repeating units in the polycarbonate, thereby replacing the Bisphenol A, of the present invention in the total amount of dihydric phenol compounds utilized. Examples of such compounds include the following:
resorcinol
4-bromoresorcinol
hydroquinone
4,4xe2x80x2-dihydroxybiphenyl ether
4,4-thiodiphenol
1,6-dihydroxynaphthalene
2,6-dihydroxynaphthalene
bis(4-hydroxyphenyl)methane
bis(4-hydroxyphenyl)diphenylmethane
bis(4-hydroxyphenyl)-1-naphthylmethane
1,1-bis(4-hydroxyphenyl)ethane
1,1-bis(4-hydroxyphenyl)propane
1,2-bis(4-hydroxyphenyl)ethane
1,1-bis(4-hydroxyphenyl)-1-phenylethane
1,1-bis(3-methyl-4-hydroxyphenyl)-1-phenylethane
2-(4-hydroxyphenyl)-2-)3-hydroxyphenyl)propane
2,2-bis(4-hydroxyphenyl)butane
1,1-bis(4-hydroxyphenyl)isobutane
1,1-bis(4-hydroxyphenyl)decane
1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane
1,1-bis(3,5-dibromo-4-hydroxyphenyl)cyclohexane
1,1-bis(4-hydroxyphenyl)cyclohexane
1,1-bis(4-hydroxyphenyl)cyclododecane
1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclododecane
trans-2,3-bis(4-hydroxyphenyl)-2-butene
4,4-dihydroxy-3,3-dichlorodiphenyl ether
4,4-dihydroxy-2,5-dihydroxy diphenyl ether
2,2-bis(4-hydroxyphenyl)adamantane
xcex1,xcex1xe2x80x2-bis(4-hydroxyphenyl)toluene
bis(4-hydroxyphenyl)acetonitrile
2,2-bis(3-methyl-4-hydroxyphenyl)propane
2,2-bis(3-ethyl-4-hydroxyphenyl)propane
2,2-bis(3-n-propyl-4-hydroxyphenyl)propane
2,2-bis(3-isopropyl-4-hydroxyphenyl)propane
2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane
2,2-bis(3-t-butyl-4-hydroxyphenyl)propane
2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane
2,2-bis(3-allyl-4-hydroxyphenyl)propane
2,2-bis(3-methoxy-4-hydroxyphenyl)propane
2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane
2,2-bis(2,3,5,6-tetramethyl-4-hydroxyphenyl)propane
2,2-bis(3-5-dichloro-4-hydroxyphenyl)propane
2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane
2,2-bis(2,6-dibromo-3,5-dimethyl-4-hydroxyphenyl)propane
xcex1,xcex1-bis(4-hydroxyphenyl)toluene
xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-Tetramethyl-xcex1,xcex1xe2x80x2-bis(4-hydroxyphenyl)-p-xylene
1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene
1,1-dibromo-2,2-bis(4-hydroxyphenyl)ethylene
1,1-dichloro-2,2-bis(5-phenoxy-4-hydroxyphenyl)ethylene
4,4xe2x80x2-dihydroxybenzophenone
3,3-bis(4-hydroxyphenyl)-2-butanone
1,6-bis(4-hydroxyphenyl)-1,6-hexanedione
ethylene glycol bis(4-hydroxyphenyl)ether
bis(4-hydroxyphenyl)ether
bis(4-hydroxyphenyl)sulfide
bis(4-hydroxyphenyl)sulfoxide
bis(4-hydroxyphenyl)sulfone
bis(3,5-dimethyl-4-hydroxyphenyl)sulfone
9,9-bis(4-hydroxyphenyl)fluorene
2,7-dihydroxypyrene
6,6xe2x80x2-dihydroxy-3,3,3xe2x80x2,3xe2x80x2-tetramethylspiro(bis)indane(xe2x80x9cspirobiindane Bisphenolxe2x80x9d)
3,3-bis(4-hydroxyphenyl)phthalide
2,6-dihydroxydibenzo-p-dioxin
2,6-dihydroxythianthrene
2,7-dihydroxyphenoxathiin
2,7-dihydroxy-9,10-dimethylphenazine
3,6-dihydroxydibenzofuran
3,6-dihydroxydibenzothiophene
2,7-dihydroxycarbazole.
The dihydric phenols (which are other than BPA) may be used alone or as mixtures of two or more dihydric phenols. Further illustrative examples of dihydric phenols include the dihydroxy-substituted aromatic hydrocarbons disclosed in U.S. Pat. No. 4,217,438.
In the polycarbonates of the present invention branching agents may optionally be used and may comprise polyfunctional organic compounds containing at least three functional groups which may be hydroxyl, carboxyl, carboxylic anhydride, haloformyl and mixtures comprising at least one of the foregoing. Specific examples include trimellitic acid, trimellitic anhydride, trimellitic trichloride, tris-hydroxy phenylethane (THPE), isatin-bis-phenol, tris-phenol TC (1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol PA (4(4(1,1-bis(p-hydroxyphenyl)-ethyl)alpha,alpha-dimethyl benzyl)phenol), 4-chloroformyl phthalic anhydride, trimesic acid and benzophenone tetracarboxylic acid, and the like. Preferably, the branching agent is tris-hydroxyphenylethane (THPE). The branching agents may be added at a level in a range between about 0 mole percent and about 0.5 mole percent, and preferably in a range between about 0.1 mole percent and about 0.5 mole percent relative to the amount of dihydric phenol.
In the polycarbonates of the present invention an endcapping agent may optionally be used. Suitable endcapping agents include monovalent aromatic hydroxy compounds, haloformate derivatives of monovalent aromatic hydroxy compounds, monovalent carboxylic acids, halide derivatives of monovalent carboxylic acids, and mixtures thereof. Examples of endcapping agents include, but are not limited to, phenol; p-tert-butylphenol; p-cumylphenol; p-cumylphenolcarbonate; undecanoic acid; lauric acid; stearic acid; phenyl chloroformate; t-butyl phenyl chloroformate; p-cumyl chloroformate; chroman chloroformate; octyl phenyl; nonyl phenyl chloroformate; or a mixture thereof. If present, the endcapping agent is present in amounts in a range between about 1 mole percent and about 6 mole percent, typically in a range between about 2 mole percent and about 5 mole percent, even more typically in a range between about 2 mole percent and about 4 mole percent relative to the dihydric phenol.
The method of preparation of polycarbonates by interfacial polymerization are well know; see for example the details provided in the U.S. Pat. Nos. 3,028,365; 3,334,154; 3,275,601; 3,915,926; 3,030,331; 3,169,121; and 4,188,314.
Although the reaction conditions of the preparative processes may vary, several of the preferred processes typically involve dissolving or dispersing the dihydric phenol reactant in aqueous caustic soda or potash, adding the resulting mixture with the siloxane to a suitable water immiscible solvent medium and contacting the reactants with the carbonate precursor, such as phosgene, in the presence of a suitable catalyst such as triethylamine and under controlled pH conditions, e.g., 8-10. The most commonly used water immiscible solvents include methylene chloride, 1,2-dichloroethane, chlorobenzene, toluene, and the like.
A catalyst may be employed to accelerate the rate of polymerization of the dihydroxy phenol reactant with the carbonate precursor. Representative catalysts include, but are not limited to tertiary amines such as triethylamine, quartemary phosphonium compounds, quaternary ammonium compounds, and the like. The preferred process for preparing resins of the present invention comprises the phosgenation reaction. The temperature at which the phosgenation reaction proceeds may vary from below 0xc2x0 C. to about 100xc2x0 C. The phosgenation reaction preferably proceeds at temperature of from room temperatures (25xc2x0 C. to 50xc2x0 C.). Since the reaction is exothermic, the rate of phosgene addition may be used to control the reaction temperature. The amount of phosgene required will generally depend upon the amount of the dihydric phenol reactant and the amount of siloxane also present.
Alternatively, the polycarbonate copolymer may be prepared by co-reacting in a molten state, the diphenolic monomers and a diaryl carbonate ester, such as diphenyl carbonate, in the presence of a transesterification catalyst in a Banbury mixer, twin screw extruder, or the like to form a uniform dispersion. Volatile monohydric phenol is removed from the molten reactants by distillation and the polymer is isolated as a molten residue.
Optionally, the polycarbonate may further include acrylonitrile-butadiene-styrene (ABS) copolymers, which are typically grafts of styrene or substituted styrenes and acrylonitrile or substituted acrylonitriles on a previously formed diene polymer backbone (e.g., polybutadiene or polyisoprene). The acrylonitrile-butadiene-styrene copolymer may typically be present in a range between about 3 weight percent and 30 weight percent, more typically in a range between about 3 weight percent and about 15 weight percent, and most typically in a range between about 3 weight percent and about 8 weight percent of the total composition.
Styrene and substituted styrenes are vinyl aromatic monomers having one or more alkyl, alkoxyl, hydroxyl or halo substituent groups attached to the aromatic ring, including, e.g., xcex1-methyl styrene, p-methyl styrene, vinyl toluene, vinyl xylene, trimethyl styrene, butyl styrene, chlorostyrene, dichlorostyrene, bromostyrene, p-hydroxystyrene, methoxystyrene and vinyl-substituted condensed aromatic ring structures, such as, e.g., vinyl naphthalene, vinyl anthracene, as well as mixtures of vinyl aromatic monomers.
Acrylonitriles are examples of xe2x80x9cmonoethylenically unsaturated nitrile monomersxe2x80x9d which are acyclic compounds that includes a single nitrile group and a single site of ethylenic unsaturation per molecule. Other monoethylenically unsaturated nitrile monomers include, for example, methacrylonitrile and xcex1-chloro acrylonitrile.
Suitable acrylonitrile-butadiene-styrene copolymers may be produced by any method known in the art. In a preferred embodiment of the present invention, a suitable ABS is a high rubber graft acrylonitrile-butadiene-styrene copolymer produced in a process which includes an emulsion polymerization step. The phrase xe2x80x9chigh rubber graftxe2x80x9d refers generally to graft copolymer resins wherein at least about 30 weight percent, preferably at least about 45 weight percent of the rigid polymeric phase is chemically bound or grafted to the elastomeric substrate phase. Suitable ABS-type high rubber graft copolymers are commercially available from, for example, GE Plastics, Inc. under the trademark BLENDEX and include grades 131, 336, 338, 360, and 415. In another preferred embodiment of the present invention, a suitable ABS is one produced in a process which includes a mass polymerization step, so-called bulk ABS.
In addition, the present invention provides shaped, formed, or molded articles comprising the polycarbonates of the present invention.
Additives may also be added to the polycarbonate product as long as they do not adversely affect the properties of the product. These additives include a wide range of substances that are conventionally added to the polycarbonates for a variety of purposes. Specific examples include anti-drip agents, heat stabilizers, epoxy compounds, ultraviolet absorbers, mold release agents, colorants, antistatic agents, slipping agents, anti-blocking agents, lubricants, antifogging agents, natural oils, synthetic oils, waxes, organic fillers, inorganic fillers and any other commonly known class of additives.
Flame retardants may optionally be used in the present invention in a range between about 2 weight % and about 8 weight % relative to the amount of the total composition. Examples of flame retardants in the present invention include phosphoramides. In one embodiment, the phosphoramide comprises a compound of the formula (II): 
wherein each Q1 is independently oxygen or sulfur; and each of A3-6 is independently an alkyloxy, alkylthio, aryloxy, or arylthio residue, or an aryloxy or arylthio residue containing at least one alkyl or halogen substitution, or mixture thereof; or an amine residue. In a preferred embodiment each Q1 is oxygen, and each A3-6 is an aryloxy moiety with at least one aryloxy moiety having at least one substituent on an aromatic ring ortho to the oxygen linkage. In a more preferred embodiment each Q1 is oxygen, and each A3-6 moiety is independently an aryloxy moiety with at least one substituent on each aromatic ring ortho to the oxygen linkage, optionally further substituted. In a still more preferred embodiment of the present invention, each Q1 is oxygen, and each A3-6 moiety is independently an aryloxy moiety with at least two substituents on each aromatic ring ortho to the oxygen linkage, as for example a 2,6-disubstituted phenoxy moiety, optionally further substituted. Preferred substituents are C1-8 straight-chain or branched alkyl, or halogen. In an especially preferred embodiment of the present invention, each Q1 is oxygen, and each A3-6 moiety is independently phenoxy, 2,6-dimethylphenoxy, 2,3,6-trimethylphenoxy, or 2,4,6-trimethylphenoxy. In a more especially preferred embodiment of the invention, each Q1 is oxygen, and all A3-6 moieties are phenoxy, 2,6-dimethylphenoxy, 2,3,6-trimethylphenoxy, or 2,4,6-trimethylphenoxy. These phosphoramides are piperazine-type phosphoramides.
Other flame retardants which may be used in the present invention include, for example, triphenyl phosphate (TPP), resorcinol diphosphate (RDP) and bisphenol-a-disphophate (BPA-DP); and mixtures thereof.
Such copolymers or resins described herein can be used for instance as: housings for computer equipment (monitors, CPUs, printers), electrical connectors, components or housings for telecomm equipment (cell phones, handheld devices), and other applications that could require transparency and flame retardance.